The present invention relates to an optical radar system which determines the respective distances from the system to detected objects and the respective directions toward the objects with respect to the system.
A conventional optical radar system adapted to be mounted on the front of an automotive vehicle includes an optical transmitter, an optical receiver, and a signal processor. The transmitter radiates a search pulse of coherent light produced by a semiconductor laser in a beam having an appropriate angle of divergence toward the object to be detected. The optical receiver collects the light pulses reflected by the object using a lens, eliminates the background noise from the collected light pulses using an interference filter and focuses the filtered light onto a single photo transducer. The resulting pulse signal from the photo transducer is amplified to an appropriate magnitude by a wide-band amplifier in the processor. A computing unit of the processor determines the distance from the radar system to the object in accordance with the delay between the arrival of the reflected pulse and the occurrence of a drive signal which triggers the transmitted pulse of coherent light, as well known in the art.
In this conventional radar system, however, the area of the light-receiving surface of the light sensitive element is very small so that the region in which the reflected pulses can be sensed is limited to a very small area forward of the optical receiver. For example, when an automotive vehicle is travelling along the axis of the transmitted pulse beam forwardly of the automotive vehicle on which the optical radar system is mounted, the distance between the preceding vehicle and the following vehicle can be computed. However, when the preceding vehicle leaves the sensible area due to a curved or sloped road, the radar system gives out information such as would be given out when there are no preceding vehicles, which is an undesirable matter.